Proportional mixer



R- E. SCHRETER ET AL Sept. 22, 1959 v PROPORTIONAL MIXER 2 Sheets-Sheet 1 Filed May 29. 1957 2 Sheets-Sheet 2 PROPORTIONAL MIXER R. E. SCHRETERY ET AL Sept. 22, 1959 Filed May 29, 1957 //VV/V705. ROBERT E. SCH/PETER ALEXA/V967? TU/ZO/A/ 3K A fORA/EKs.

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being fired, etc.

Unite PROPORTIONAL MIXER Robert E. Schreter, Richmond Hills, and Alexander J.

Turpin, Stewart Manor, N'.Y., assignors to Hauck Manufacturing Co., Brooklyn, N.Y., a corporation of New York Application May 29, 1957, Serial No. 662,372

14 Claims. (Cl. 48-184) Other objects Sttes Fatent is externally accessible and readily made without disassembly of the mixer.

A further object of the invention is to provide a mixer of the Venturi type, in which the constriction at the throat is variable, and in which the constriction at the low volume (low capacity or combustion rate) adjustment is kept localized at or near the suction gas connection. This localization is desirable for maximum efliciency, and for linearity or uniformity of gas-to-air ratio.

To accomplish the foregoing objects, and other objects which will hereinafter appear, our invention resides in the mixer elements, and their relation one to another, as are hereinafter more particularly described in the following specification. The specification is accompanied by drawings in which:

Fig. 1 is a view drawn to small scale showing a burner system using the mixer;

Fig. 2 is a longitudinal section through a mixer embodying features of our invention;

Fig. 3 is a fragmentary section similar to a part of Fig. 2, but showing the mixer adjusted for maximum capacity;

Fig. 4 is a fragmentary view of a frusto-conical diaphragm forming a part of the invention;

Fig. 5 is a longitudinal section similar to Fig. 2, but showinga modification;

Fig. 6 is a fragmentary section generally similar to 'Fig. 5, but showing the mixer adjusted for maximum capacity; and

' Fig. 7 is a fragmentary section through still another modification of the invention.

Referring to the drawing, and more particularly to Fig. l, the mixer M is here used in a combustion system which comprises a gas supply pipe 12, a constant or zero pressure regulator 14 in said pipe, an air supply pipe 16, and one or more throttles 18 and 20 to control the air and to thereby control the combustion rate. The pressure regulator preferably has a long sensitive spring, housed at 15. The throttle 20 is manually adjustable, and in some installations the control is manual, there being no throttle corresponding to that shown at 18. r The throttle 18 is automatically controlled by any suitable means, here indicated at 22. Such means may be responsive to the steam pressure of a boiler being fired, or to the temperature within a heat treatment furnace The mixture of fuel and air is supplied through pipe 24 and appropriate branch pipes to one or more burners. In the present case, there are four burners indicated ,at 26, 28, 30 and 32. These are all controlled'in unison in the system here illustrated. The mixer M is shown disposed in vertical position in Fig. 1, but it may Patented Sept. 22, 1959 be disposed in any desired direction, and is illustrated in horizontal position in the remaining figures of the drawmg.

Referring now to Fig. 2, the mixer comprises a housing 34, providing a Venturi passage 36 which has a diffuser 38 centered axially thereof. The diffuser tapers in the direction of flow in order to provide an annular Venturi passage of expanding section. The air is supplied at inlet 40, while gas is supplied at a gas connec tion 42. The gas is led to an annular gas suction or throat region, generally designated 44. A fixed adjustable valve means, here indicated as a poppet valve 46, is preferably provided in the gas supply line ahead of the suction connection at 44, in order to vary the gas-to-air ratio. Such an adjustment is not new. In the present case, this is readily done externally by rotation of the threaded stem 48 of the poppet valve, Which is shown in an intermediate position. Raising the valve moves it toward the seat, and reduces the gas-to-air ratio.

In accordance with the present invention, we provide an externally accessible means, specifically a threaded rod 50, to vary the constriction of the Venturi passage at the throat region, and to thereby vary the capacity of the burner. The mechanism for this purpose includes a collapsible device 52 of variable diameter located at the throat portion of the Venturi passage. The rod 50 functions to vary the effective diameter of the collapsible device 52, as will be seen by the change from Fig. 2 to Fig. 3.

In Figs. 2 and 3, the collapsible device 52 is a frustoconical variable-diameter diaphragm made of resilient material, and tending normally to expand or flatten. It is bent to conical shape by means of ring 54 which works on or bears against the diaphragm to bend it. In lieu of a ring there could be a series of fingers or links connected to the spokes. It will be evident that relative axial movement of working means or ring 54 and diaphragm 52 will change the angle of the cone and the effective diameter of the diaphragm, and thus the annular cross section area of the Venturi passage at the throat.

The particular variable diameter diaphragm here shown is made of resilient sheet metal. There are a plu rality of laminations, in this case two laminations 56 and 58, shown fragmentarily to enlarged scale in Fig. 4. Each lamination is a disc which is radially slit or cut away, as indicated at 60 for the front lamination 58, leaving broad radial spokes 62. The rear lamination 56 is similarly cut away, as indicated between the broken lines 64, thus leaving broad radial spokes 66. The discs are rotationally displaced from one another, so that the parts 62 cover the triangular slits 64, and similarly the parts 66 cover the triangular slits 60. It will be'evident that with this construction, the diaphragm is readily adjusted between the contracted position shown in Fig. 3, and the expanded position shown in Fig. 2. It is also evident that the spokes 62 and 66 could be pivoted near the center, instead of being resilient as shown.

In the specific construction here shown, the adjusting rod 50 is a threaded rod which carries the difluser 38, these parts being fixedly secured together, as by means of a force fit connection at 68 (Fig. 2). The diaphragm 52 is disposed immediately behind diffuser 38, and is held thereagainst by means of a compression spring 70. The ring 54 is formed at the end of a member 72 which diverges toward and forms an approach to the diffuser 38. The part 72 is hollowed, as shown at 74, to make room for the compression spring 70, and for the diaphragm When it is pulled to the left. The member 72 with its ring 54 is stationary, and may abut a bearing 76 forming a part of the housing of the mixer. Bearing 76 may, if de-.

- sired, be supported by a web 78, which acts also as a flow straightening fin for air entering at 40'.

The threaded rod 50 is received in an internally threaded bushing 80, which may be secured to the housing, as by means of a force fit, welding, threaded connection, or other manner. The end of rod 50 may be slotted to receive a screwdriver, or it may be provided with flats to receive a wrench.

It will be seen that in the arrangement of Figs. 2 and 3, the diffuser 38 carries a means 52 to vary the effective area of the annular throat, and to thereby vary the capacity of the mixer. This means 52 is changeable -be tween smaller and larger diameters over a desired range, and it tends of itself to assume a diameter at one end of the range. The externally accessible means 50 is used to change the means 52 toward the other end of the range.

A modified form of the invention is shown in Figs. 5 and 6 of the drawing. Here again, there is a Venturi housing 82 providing a Venturi passage 84, in which a diff-user 86 is centered. Air is supplied at inlet 88, and gas is supplied at connection 90. This leads to an annular suction-inlet 92 at the throat of the Venturi passage. A fitting is assembled to housing 82 by means of bolts at 94, and may be exactly like that shown in Fig. 2, which is an L which preferably also includes a poppet valve to vary the gas supply opening, and thus to vary the gas-to-air ratio.

To vary the capacity of the mixer, we again provide a frusto-conical variable-diameter diaphragm 96, which again tends resiliently to move to one end of the range. In the present case, the small end of the diaphragm -is movable, while the large end 98 is stationarily mounted in the housing. Here again, the iris-like diaphragm preferably comprises a plurality of laminations of thin resilient sheet metal, and the conical part of each lamination is slit to facilitate the desired'motion, but the several laminationsare rotatably displaced so that together theyform a continuous diaphragm, much as previously described. The part 98 may be formed on one lamination, and a smaller part 97 on the other, the former holding thelatter in position.

The ring which works on or controls the diaphragm is indicated at 100. It is mounted on and moved with the diffuser 86, it being carried by a few spaced webs 102. It will be evident from comparison of Figs. 5 andfi that when ring 100 is moved --to the left, as in Fig. 5, the diaphragm contracts and minimizes the eifective'th-roat area of the Venturi passage. When the ring is movedto the right, as shown in Fig. 6, the ring 96 expands the diaphragm to the maximum diameter permitted by the part 104 of the housing, and thus the-throat area of the Venturi passage is-made-a maximum.

The diffuser may be moved axially in the same way as previously described, there being an externally-accessible threaded rod 106 which is connected to the diffuser, and which is threadedly received in a bushing 108. The latter is fixedly mounted in a plate 110 which closes one end of the mixer housing, and which may be secured 'by screws, not shown.

Still another form of the 'invention'is illustrated in Big. 7 of the drawing. In this case, the collapsible device of variable diameter is indicated at 112. It consists of a generally cylindrical plug of a material having the-characteristics of rubber. However, it is preferred to useneoprene or a compressible plastics material which will not be afiected by the highertemperatures which may be encountered in equipment used near a boiler, furnace, ;or burner.

The mixer housing 114 may resemble that shownin Figs. 2 and 3 of the drawing. It provides a Venturi passage 116, in which a diffuser 118 is disposed. As before, the-diffuser is fixedly connected at 12% to a rod 122 which is externally accessible, and .axially adjustable, much as previously described in Figs. 2 and 3'. The plug 112 is disposed between the movable ditfuser 4 118, and a stationary approach member 124, which backs against bearing 126, preferably supported by a flowstraightening web 128, as previously described.

It will be evident that axial pull on rod 122, caused by screwing the same in outward direction, will shift diffuser 118 from the solid line position 118 to the broken line position 118, and this will at the same time compress the plug 112 in axial direction, thereby causing it to expand in radial direction, as indicated by the broken convex lines 112'. Thus, the effective diameter of the plug is increased, and the throat area of the Venturi passage is decreased, thereby varying the capacity of the mixer.

If desired, the resilient member 112 may be received between antifriction washers 113, thereby facilitating relative rotation. However, this is not essential, particularly if the surfaces at between the parts 124 and 125 are kept smooth, for in such case all of the parts up to the bearing 1% may rotate in unison.

It will be understood that a gas inlet and valve fitting may be added at 130, this being secured by screws re,- ceived in threaded holes 132. The fitting and valvearrangement may be exactly as shown and described in con,- nection with Fig. 2.

One important advantage of the mixers here shown is that the throat or minimum area of the Venturi passage is keptnear the gas suction port orv gas inlet, particularly when the capacity of the mixer is reduced to a small value. Thus, in Fig. 2, the periphery of the diaphragm 52is localized immediately .at the gas suction inlet 44. In Fig. 3, when the iris diaphragm is retracted axially away from the inlet 44, it is of minimum diameter; the passage is of maximum area; and the axial displacement is therefore of no consequence. In the arrangement of Figs. 5 and'6, the free edge of the diaphragm may be disposed as :close as desired to thegas inlet :92, and remains in that position during opening or closing of the diaphragm. In Fig. 7, the maximum diameter portion of the resilient plug 112 is located closeto the gas inlet when gtheplug is expanded radially, as shown in broken lines.

lt is believed that the construction and operation, as Well as the advantages of our improved proportional mixer, will be apparent from the foregoing detailed ,description. The mixer receives air ata pressure of from, say one-half pound to three pounds, and automatically mixes it with gas which may be supplied at a pressure of from, say two to eight inches of water, but the gas pressure preferably is preliminarily reduced :to Zero. kit is the energy of the moving air which induces the gas-flow, and thus the amount of gas drawn in varies directly as the a'mountof air flowingthrough the mixer. The volume or combustion rate at any instant is controlled by operation .of a single valve, this being'a throttle in the air supply. The throttle control maybe a butterfly valve with an indicating pointer and dial, so that the settings canbe duplicated. It is also well adapted for automatic control. The ratio is readily adjustableby externally accessible means. The range or capacity of the mixer is also externally adjustable.

The mixer is simple, rugged, inexpensive to :manufacture, and dependable in operation. The constrictionor throat of the Venturi passage remains near the gas :suc- .tion connection, even at minimumcapacity.

With reference .to Fig.2 of the drawing, it will be .understood that .the diaphragm COUldrbE controlled by moving-the ringSA by .means of the screw 50, the diaphragm remaining istationary in :axial direction, .or for that .matter, rby relativelymovingfboth .the ring .andthe diaphragm toward or away from one another. With referencelto Fig. 5,:-it will be understood thatthe ring mightibe moved axially thy means of an adjusting screw Without necessarilygmoving the diifuser too, andfurther, that the'ring might be=stationary and the diaphragm might be moved axially-instead of versa.

With reference to the arrangement shown in Fig. 7, it will be understood that the compressible plug might be squeezed from left to right, instead of from right to left, or might be oppositely squeezed by simultaneous movement at both ends.

These and other changes may be made in the structures shown, and it will therefore be understood that while we have shown the invention in several preferred forms, changes may be made without departing from the scope of the invention, as sought to be defined in the following claims.

We claim:

1. In a combustion system, a mixer to combine gaseous fuel and air, said mixer comprising a housing providing a first connection for gaseous fuel, a second connection for air, and a Venturi passage for receiving both fuel and air and having a diffuser centered axially thereof, said diffuser and housing tapering relative to one another to provide an annular Venturi passage of expanding section in the direction of flow, an externally accessible means to vary the constriction of the annular Venturi passage at the throat, and to thereby vary the capacity of the mixer, said means including a collapsible device of variable diameter located at the throat, a rod, and means carried by said rod to vary the diameter of said collapsible device.

2. A mixer to combine two gases, said mixer comprising a housing providing a first connection for one gas and a second connection for the other gas, and a Venturi passage for receiving both gases and having a difiuser centered axially thereof, said difluser and housing tapering relative to one another to provide an annular Venturi passage of expanding section in the direction of flow, an externally accessible means to vary the constriction of the annular Venturi passage at the throat, and to thereby vary the capacity of the mixer, said means including a collapsible device of variable diameter located at the throat, means to shift the difiuser axially, and means carried by said diifuser and operative by axial movement of the diffuser to vary the diameter of said collapsible device.

3. A mixer to combine two gases, said mixer comprising a housing providing a Venturi passage having a diffuser centered axially thereof, said diffuser tapering in the direction of flow to provide an annular Venturi passage of expanding section, means carried by said diffuser to vary the effective area of the annular throat and to thereby vary the capacity of the mixer, said means carried by said diffuser being physically changeable relative to the diffuser between smaller and larger diameters over a desired range, and an externally accessible device to change the diameter of said means.

4. A mixer to combine two gases, said mixer comprising a housing providing a Venturi passage, a means to vary the constriction of the Venturi passage at the throat, and to thereby vary the capacity of the mixer, said means including a frusto-conical diaphragm, means working on said diaphragm to change the angle of the cone whereby relative axial movement of the working means and diaphragm changes the diameter of the diaphragm, and means to cause said relative axial movement in order to vary the effective area of the annular throat and to thereby vary the capacity of the mixer.

5. A mixer to combine two gases, said mixer comprising a housing providing a Venturi passage, a means to vary the constriction of the Venturi passage at the throat, and to thereby vary the capacity of the mixer, said means including a frusto-conical diaphragm made of a plurality of laminations of resilient sheet metal, each diaphragm being radially slit, and the slits of one lamination being displaced relative to another to provide a continuous diaphragm, said diaphragm tending to bend in one direction, a ring bearing against said diaphragm to bend it in opposite direction whereby relative axial movement of the ring and diaphragm changes the diameter of the diaphragm, and means to cause said relative axial movement in order to vary the efiective area of the annular throat and to thereby vary the capacity of the mixer.

6. A mixer to combine two gases, said mixer comprising a housing providing a Venturi passage having a dilfuser centered axially thereof, said diffuser tapering in the direction of flow to provide an annular Venturi passage of expanding section, a means to vary the constriction of the Venturi passage at the throat, and to thereby vary the capacity of the mixer, said means including a frusto-conical diaphragm made of a plurality of laminations of resilient sheet metal, each diaphragm being radially slit, and the slits of one lamination being displaced relative to another to provide a continuous diaphragm, said diaphragm tending to bend in one direction, a ring bearing against said diaphragm to bend it in opposite direction, whereby relative axial movement of the ring and diaphragm changes the diameter of the diaphagm, and a threaded rod to cause said relative axial movement in order to vary the effective area of the annular throat and to thereby vary the capacity of the mixer.

7. A mixer as defined in claim 6 in which the frustoconically shaped diaphragm is carried at its small diameter end by the diffuser.

8. A mixer as defined in claim 6 in which the frustoconical-ly shaped diaphragm is carried by the diffuser and is axially movable with the dilfuser and normally expands to maximum diameter, and in which the ring is stationary.

9. A mixer as defined in claim 6 in which the frustoconically shaped diaphragm is stationary, and in which the ring is carried by the difiuser and is axially moved with the diifuser.

10. A mixer as defined in claim 4 in which the large end of the frusto-conically shaped diaphragm is of constant diameter, and in which the small end of the diaphragm is of variable diameter, and in which the ring bearing against the diaphragm varies the small end of the diaphragm.

11. A mixer as defined in claim 5 in which the large end of the frusto-conically shaped diaphragm is of constant diameter, and in which the small end of the diaphragm is of variable diameter, and in which the ring bearing against the diaphragm varies the small end of the diaphragm.

12. A mixer as defined in claim 6 in which the large end of the frusto-conically shaped diaphragm is fixedly mounted in the housing, and in which the diaphragm tends to contract to minimum diameter, and in which the ring is carried on the difl'user by a few spaced webs which do not interrupt flow of air around the diffuser, said ring being axially movable with the diffuser and bearing against the inside of the diaphragm to expand the same to maximum diameter.

13. A mixer as defined in claim 1, in which the variable diameter means includes a generally cylindricalplug of resilient material having the compressible elastic char acteristics of rubber, and in which the rod squeezes said plug axially and thereby expands the diameter of the plug.

14. A mixer as defined in claim 2, in which the variable diameter means includes a generally cylindrical plug of resilient material having the compressible elastic characteristics of rubber, and in which the means to shift the diffuser squeezes said plug axially between the diffuser and a stationary approach surface leading to the diflIuser and thereby expands the diameter of the plug.

References Cited in the file of this patent UNITED STATES PATENTS 1,110,041 Christian Sept. 8, 1914 1,399,459 Bird Dec. 6, 1921 2,366,322 Foster Jan. 2, 1945 2,507,680 Rheude May 16, 1950 2,524,559 Campbell Oct. 3, 1950 

1. IN A COMBUSTION SYSTEM, A MIXER TO COMBINE GASESOUS FUEL AND AIR, SAID MIXER COMPRISING A HOUSING PROVIDING A FIRST CONNECTION FOR GASEOUS FUEL, A SECOND CONNECTION FOR AIR, AND A VENTURI PASSAGE FOR RECEIVING BOTH FUEL AND AIR, AND HAVING A DIFFUSER CENTERED AXIALLY THEREOF, SAID DIFFUSER AND HOUSING TAPERING RELATIVE TO ONE ANOTHER TO PROVIDE AN ANNULAR VENTURI PASSAGE OF EXPANDING SECTION IN THE DIRECTION OF FLOW AN EXTERNALLY ACCESIBLE MEANS TO VARY THE CONSTRICTION OF THE ANNULAR VENTURI PASSAGE AT THE THROAT, AND TO THEREBY VARY THE CAPACITY OF THE MIXER, SAID MEANS INCLUDING A COLLAPSIBLE DEVICE OF VARIABLE DIAMETER LOCATED AT THE THROAT, A ROD, AND MEANS CARRIED BY SAID ROD TO VARY THE DIAMETER OF SAID COLLAPSIBLE DEVICE. 